Method for removing sulfur compounds from sour gas streams and hydrogen rich streams

Abstract

The present invention relates to a process for purifying a gas stream comprising hydrogen sulfide or mercaptans, or mixtures thereof. The gas stream can be a sour natural gas stream, a landfill gas or an industrial gas stream. The process comprises contacting the gas stream at effective absorption conditions including an absorption temperature less than about 300° C. with a solid absorbent effective to absorb the hydrogen sulfide, or mercaptans or mixtures thereof to provide a purified gas stream. Method is useful for treating gas streams having up to 90 vol-% hydrogen sulfide, or treating highly pure hydrogen streams. The invention is useful as a guard bed for fuel cells and sensitive laboratory instruments. The invention can also be employed to treat steam reformer product hydrogen streams without the need for further compression of the product hydrogen streams.

We claim: 
     
         1 . A process for sweetening a sour gas stream to provide a sweetened gas stream, said process comprising contacting the sour gas stream comprising hydrogen or methane and a sour impurity selected from the group consisting of hydrogen sulfide, mercaptans and mixtures thereof at effective absorption conditions including an absorption temperature less than or equal to 300° C. with a solid absorbent comprising a copper oxide and having a copper content greater than or equal to 50 wt-% and a zinc content less than 0.3 wt-%, said solid absorbent being selective for the regenerable absorption of said sour impurity to absorb at least a portion of the sour impurity to provide the sweetened gas stream having a reduced amount of the sour impurity. 
     
     
         2 . The process of  claim 1 , wherein the sour gas stream is a sour natural gas stream or a landfill gas stream or an industrial gas stream or a hydrogen gas stream. 
     
     
         3 . The process of  claim 1 , wherein the sour gas stream is a hydrogen stream comprising hydrogen sulfide and the sweetened gas stream comprises less than 10 ppbv hydrogen sulfide. 
     
     
         4 . The process of  claim 1 , wherein the sour gas stream is a sour natural gas stream or a landfill gas stream and comprises less than about 90 vol-% hydrogen sulfide. 
     
     
         5 . The process of  claim 1 , wherein the solid absorbent is a crude copper compound selected from the group consisting of copper carbonate, copper oxychloride, copper hydroxide, copper oxide, copper sulfide and copper sulfate which has been activated by roasting at a roasting temperature of from about 380° C. to about 800° C. 
     
     
         6 . The process of  claim 5 , wherein the roasting temperature is from about 380° C. to about 600° C. 
     
     
         7 . The process of  claim 5 , wherein the roasting temperature is from about 400° C. to about 450° C. 
     
     
         8 . The process of  claim 5 , wherein the solid absorbent has an average particle size ranging from about 4760 to about 149 microns and an average apparent bulk density of from about 1.1 to about 1.6 g/cc, an interior void volume of from about 53 to about 66 percent, and an average pore volume of about 0.14 cm 3 /g. 
     
     
         9 . The process of  claim 1 , wherein the solid absorbent is regenerable or recyclable. 
     
     
         10 . The process of  claim 1 , wherein the solid absorbent is regenerated by contacting said solid absorbent with a regeneration gas stream comprising oxygen at an effective regeneration temperature between about 300° C. to about 600° C. 
     
     
         11 . The process of  claim 3 , wherein the hydrogen stream comprises from 95.0 to 99.999 vol-% hydrogen and the sweetened gas stream comprises less than 6 ppbv hydrogen sulfide. 
     
     
         12 . The process of  claim 11 , wherein the sweetened gas stream comprises less than 3 ppbv hydrogen sulfide. 
     
     
         13 . The process of  claim 3 , wherein the absorption temperature comprises less than or equal to 30° C. 
     
     
         14 . The process of  claim 5 , wherein the solid absorbent selective for the absorption of hydrogen sulfide is a copper carbonate selected from the group consisting of Cu 2 (CO 3 )(OH) 2 , Cu 3 (CO 3 ) 2 (OH) 2 , and mixtures thereof. 
     
     
         15 . The process of  claim 14 , wherein the copper carbonate has a copper content greater than or equal to 80 wt-% of the theoretical copper content of the copper carbonate. 
     
     
         16 . The process of  claim 14 , wherein the copper carbonate has a copper content of between about 90 wt-% and 99.99 wt-% of the theoretical copper content of the copper carbonate. 
     
     
         17 . The process of  claim 1 , wherein the effective absorption temperature ranges from ambient to less than or equal to about 300° C. 
     
     
         18 . The process of  claim 1 , wherein the effective absorption temperature ranges from ambient to less than or equal to about 100° C. 
     
     
         19 . The process of  claim 1 , further comprising terminating the contacting of the solid absorbent with said sour gas stream and regenerating the solid absorbent by contacting the solid absorbent with a regeneration gas at an effective regeneration temperature to desorb at least a portion of the absorbed impurity and provide a spent regeneration stream, and purging the solid absorbent with an inert gas stream to purge the solid absorbent of any residual oxygen prior to recontacting the solid absorbent with the sour gas stream. 
     
     
         20 . The process of  claim 19 , wherein the regeneration gas is selected from the group consisting of air, oxygen mixed with a non-reactive gas, or oxygen. 
     
     
         21 . A continuous process for the sweetening of a sour gas stream comprising water, hydrocarbons, entrained particles, and hydrogen sulfide to provide a sweetened gas stream, said process comprising:
 a) passing the sour gas stream to a heater-dryer to remove at least a portion of the water from the sour gas stream or heat the sour gas stream above its dew point to provide a dried gas stream;   b) passing the dried gas stream to a filter zone to remove at least a portion of the entrained particles to provide a filtered gas stream;   c) passing the filtered gas stream at effective absorption conditions including an absorption temperature less than about 300° C. to at least one absorption bed of a plurality of absorption beds containing a regenerable absorbent selective for the absorption of hydrogen sulfide to provide the sweetened gas stream;   d) terminating step (c) in at least one of the absorption beds and regenerating the regenerable absorbent by contacting said regenerable absorbent with a regeneration gas comprising air or oxygen at an effective regeneration temperature to desorb at least a portion of the absorbed impurity and provide a spent regeneration stream;   e) purging the at least one absorbent bed with an inert gas stream to purge the at least one absorbent bed of any residual oxygen; and,   f) resuming step (c) in the at least one absorption bed.   
     
     
         22 . A process for sweetening a sour gas stream comprising hydrogen or methane and a sour impurity selected from the group consisting of hydrogen sulfide, mercaptans and mixtures thereof to provide a sweetened gas stream comprising less than 6 ppbv hydrogen sulfide and mercaptans, said process comprising passing the sour gas stream at an absorption temperature comprising less than 40° C. to a guard bed containing a solid absorbent containing a roasted copper compound having an average apparent bulk density of from 1.1 to about 1.6 g/cc, an interior void volume of from about 53 to about 66 percent, and an average pore volume of about 0.14 cm 3 /g, wherein said roasted copper compound was prepared by roasting a crude copper compound comprising a natural or synthetic copper compound having an original crystal structure and a zinc content less than 0.3 wt-% at a roasting temperature above about 380° C. and below about 800° C. effective to remove at least a portion of water and carbon dioxide from the copper compound while retaining at least a portion of the original crystal structure and withdrawing the sweetened gas stream. 
     
     
         23 . The process of  claim 22 , wherein the natural or synthetic copper compound has a copper content between about 90 wt-% and less than or equal to about 99.99 wt-% of the theoretical copper content of the crude copper compound. 
     
     
         24 . The process of  claim 22 , wherein the natural or synthetic copper compound is selected from the group consisting of copper carbonate, copper hydroxide, copper oxychloride, copper sulfide, copper sulfate and mixtures thereof. 
     
     
         25 . The process of  claim 22 , wherein the natural or synthetic copper compound is a copper carbonate. 
     
     
         26 . The process of  claim 22 , wherein the guard bed further comprises one or more adsorption beds containing one or more cylindrical tubes having an inlet and an outlet and containing said solid adsorbent, whereby when the sour gas stream is passed through the one or more adsorption beds, the sweetened gas is provided. 
     
     
         27 . The process of  claim 22 , wherein the sour gas stream is a hydrogen stream comprising hydrogen sulfide and the sweetened gas stream comprises less than 10 ppbv hydrogen sulfide.